The production of novelty yarns has long been a major objective in the textile and carpet industry. These yarns are commercially valuable as they provide unique and desirable aesthetics to their end use articles. One such novelty yarn, nub yarn, refers to a yarn containing small lumps, knots or specks which have been introduced into the main fiber. Nub yarns are sometimes referred to as slub yarns, however nubs are generally shorter and more compact and thus have a larger diameter to length ratio than do slubs.
The presence of large slubs is undesirable for certain end uses where the aesthetics are more dependent on a low variability in slub size as well as an absence of large slubs.
Carpet containing small nubs is generally made from staple and the nubs are not tightly adhered to the core fiber. This type of carpet can be used only in low traffic areas, since the nubs are held in place only by the friction restraint of the twist. In a high traffic area, these carpets would quickly lose their nubs and the corresponding desirable aesthetic appearance.